Use the following arrow speed calculator to estimate arrow speed.
- IBO Standards
- 30 inch draw length
- 70 pound draw weight
- 350 grain arrow
- +/- 1 inch change in draw length ~ +/- 10 FPS
- +/- 10 pound change in draw weight ~ +/- 18 FPS
- +/- 3 grain change in arrow weight ~ +/- 1 FPS
- +/- 3 grain change in string weight ~ +/- 1 FPS
Factors That Affect Speed
By Bob Robb
While there are other factors to consider when setting up a compound bow for hunting, all bowhunters want to shoot as fast an arrow as they can with their bow setup. The arrow speed calculator above provides a quick estimation. A fast arrow has the flattest trajectory possible, and that’s a good thing, for several reasons, the biggest being the leeway in aiming at a distant target at an unknown range.
There are several factors that go into the arrow speed equation. When shooting a compound bow, all things being equal, they are:
- Draw weight: The more draw weight you pull, the faster the arrow will fly. The rule of thumb is that for every 10 lbs. of draw weight your bow is reduced, raw arrow speed is reduced 15-20 fps.
- Draw length: A longer draw length creates a longer power stroke than a shorter draw length, allowing the bow to store more energy. The rule of thumb was that for every added inch of draw length, you increase raw arrow speed by approximately 10-15 fps.
- Arrow weight: Again, the rule of thumb is that for every 5 grains of added arrow weight, you will drop raw speed by 1-2 fps.
- Bowstring weight: Adding weight to a bowstring (peep sight, string silencers, string loop) will affect raw speed, but not by much. Generally speaking, adding 20 grains of overall weight to the string will only deduct about 5 fps off the raw arrow speed.
Many bowhunters don’t quite understand the complexity behind bow speeds. They see a bow’s IBO speed rating listed, and assume they will get that raw arrow speed, or maybe a little better if they buy that bow. But that rarely happens, and here’s why.
The standard method of estimating – and selling – the raw arrow speed of a compound bow is complex and specific. The IBO method (detailed in the arrow speed calculator instructions above) sets up a bow and an arrow weighing 5 grains per lb. of draw weight. Another common speed rating is the ATA rating, which uses a 30-inch draw length, 70 lb. draw weight, and 350-grain arrow. Thus, when a manufacturer touts its bow as having a speed of, say, 350 fps, the truth is that a hunting weight arrow of 400-450 grains from that same bow will initially leave the bow much slower – especially if the draw weight and draw length are significantly reduced.
In closing, using an arrow speed calculator will provide a solid estimate; however, you have to shoot your hunting weight arrow through a chronograph to know exactly how fast it is flying. And remember, in bowhunting speed is good – but it is far from everything.
More on Speed
Arrow Speed Calculator Example
My bow stayed the same: 60-pounds at 27.5-inches of draw. To make the change in arrow, I went back to our Arrow Efficiency Calculator. Knowing I shot my 315-grain antelope arrow at 309 FPS, I entered that data to find the most efficient arrow weight for my new whitetail arrow. The results suggested a weight between 400- and 428-grains. With the disadvantage of my short draw length of 27.5-inches and my draw weight of 60-pounds because of a bad shoulder, I decided to go with the fastest arrow within that range, something right around 400-grains.OK? Okay, Time for a New Arrow | Darren Choate
Arrow Speed Calculator Example
Chasing 300 fps? I remember when I first started bowhunting; it was right around the time I became a teenager. During my teens, I spent countless hours with my dad in our “archery shop,” building arrows, tuning bows, and then testing their performance right outside in our backyard. At the time — let’s call it the Round Cam Epoch — the chase was for 200 fps. About the time I reached my father’s then age, technology changed drastically, making it possible for bow companies to achieve 300 fps with a hunting bow. Not too long after that came the advent of the ‘speed bow,’ and soon, almost every bow on the market was capable of hurling an arrow at 300 fps. Now, there are a few bows rated at 350+ fps based on the International Bowhunting Organization’s (IBO) standard. The IBO standard began as a means to regulate archery competitions, but the majority of bow companies have adopted its guidelines to standardize the measurement of arrow speed for the purposes of setting bow specifications.Chasing 300 FPS for the Little Guy | Darren Choate